Dielectrics are commonly used in semiconductor devices for isolation and charge storage. Undesirable charge accumulation can occur on the surface of the device coated with a dielectric as well as on intermediate layers that are capacitively coupled to the surface. Such charge accumulation can occur during manufacturing of the device, (e.g. through reactive ion etching and other steps employing electric fields) or part assembly. Charge accumulation can also occur while the device is being used following manufacturing (e.g. from stray electromagnetic coupling). Accumulated charge on a semiconductor surface can persist for a significant duration depending in part on environmental factors such as temperature and humidity.
Accumulated charge is responsible for many deleterious effects including the introduction of electric field offsets (e.g. stiction), thin oxide tunneling, oxide breakdown, and the formation of conductive channels between transistor terminal junctions. As device geometries continue to shrink for microsensors, microactuators, and semiconductors in general, coupled with increased performance demands, the level of tolerable charge accumulation continues to decrease. Current methods to prevent charge accumulation rely on shielding of the entire device, thus requiring additional isolation and costly processing steps. Other methods are limited to protecting the device only during manufacturing.